Use of iron- or zinc-based nanostructured compounds in drilling fluids for h 2s sequestration

Abstract

The present invention relates to the use of iron- or zinc-based nanostructured compounds developed for use in water-based drilling fluids (WBDFs) and non-aqueous drilling fluids (NDFs). Furthermore, the present invention evaluates the H2S sequestration capacity of these nanostructured compounds and compares them to conventional metallic oxides and to other currently used sequestrants.

Description

USE OF NANOSTRUCTURED IRON OR ZINC BASED COMPOUNDS IN DRILLING FLUIDS FOR H2S SEQUESTRATION Field of the invention

[0001] The present invention belongs to the technical field of oil exploration and production; more specifically, Well Drilling and Completion.

[0002] The present invention relates to the innovative application of products based on nanostructured compounds based on iron or zinc that are added to drilling fluids for hydrogen sulfide (H2S) sequestration. Background of the invention

[0003] Hydrogen sulfide (H2S) is frequently found in oil and gas geological formations. This compound is corrosive to equipment used in well drilling, such as drill pipe, and to well casing. When a drill pipe ruptures due to hydrogen sulfide embrittlement (due to a phenomenon called Sulfide Stress Corrosion (SSC)), the drilling operation must be stopped and the drill pipe string repaired. H2S is also an environmental pollutant and an occupational hazard for operators involved in drilling and well completion activities. Low concentrations of hydrogen sulfide produce irritation of the conjunctiva and mucous membranes, headaches, dizziness, nausea, and lassitude. Exposure to high concentrations can result in death. Therefore, its removal from oil is essential and must be done as early as possible in the production process.

[0004] In offshore exploration and production fields In oil, H2S is often found in large quantities. Therefore, oil companies and the scientific community are concerned about developing research and technologies to remove it during the crude oil extraction process. In this context, companies have preferred to mitigate the concentration of hydrogen sulfide gas before the oil reaches the platform; that is, along the production column, due to the risk of pipe corrosion.

[0005] Among the practices adopted to remove hydrogen sulfide from petroleum, the application of chemical scavengers stands out. These compounds react with the contaminant, removing it from its free form in the fluid and, consequently, reducing its aggressiveness.

[0006] There are several types of scavengers available on the market, but selecting the best one is not trivial. The chemical compound must possess important characteristics such as selectivity and reversibility of the reaction with H2S.

[0007] In oil fields producing large volumes of gas, the cost of the H2S sequestration process can be substantial, millions or even tens of millions of dollars per year.

[0008] In general, there are two categories of scavengers: regenerative and non-regenerative. In regenerative scavengers, H2S absorption is reversible; however, this type of scavenger is not typically used in oil production fields. Non-regenerative scavengers are more applicable in these cases and can be divided into several categories, such as: basic metal solids; oxidizing chemicals; aldehydes and their related products; metal carboxylates and chelates (which may be regenerative); reaction products of aldehydes with amines, including triazines; and other amine-based products.

[0009] Solid scavengers are generally based on iron or zinc oxides and cannot be injected in liquid form. The resulting products are mostly hydrophilic, which facilitates their adhesion to water and, consequently, their greater H2S removal efficiency. Liquid scavengers are generally atomized and can be inserted at any point in the production line.

[0010] Aldehyde scavengers are capable of sequestering H2S to form various sulfur compounds. Typical aldehydes that stand out as scavengers are formaldehyde, glutaraldehyde, acrolein, and glyoxal. Triazines are also important scavenging agents, but they result from the reaction of aldehydes with amines.

[0011] Thus, given so many possibilities, it is essential to study in depth the nature of the sequestrant and its injection site, since these variables determine the efficiency and cost of sequestration (ALMEIDA, 2013; KELLAND, 2014).

[0012] The purpose of adding iron or zinc compounds to drilling fluids is to sequester H2S through iron or zinc sulfide formation reactions. However, in this case, the consumption of the sequester product is high, and the cost of such input is high. significantly high in operations.

[0013] Since the reaction between H2S and iron and zinc oxides occurs primarily and at a faster rate on the solid's surface, increasing the scavenger's surface area through the use of nanostructures becomes a viable strategy for increasing scavenger availability for reaction and, therefore, improving performance. Additionally, it is known that during an H2S abatement operation in drilling fluids, the reaction between the scavengers and acid gas (H2S) is hindered by the presence of other components in the drilling fluid, such as starches, gums, and other polymers, substances capable of passivating the scavenger's surface.

[0014] The larger area / volume ratio typical of nanostructures provides a larger mass available for sulfide reaction when compared to larger structures, therefore, it is possible to reach the same amount of H2S sequestered using a smaller mass of sequestrant, bringing gains in logistics (transportation and storage) and reduction of environmental impact (less use of metals in the process).

[0015] In order to increase the reactivity of the H2S scavenging agent and reduce its quantity used, the present invention uses and evaluates the H2S scavenging capacity of nanostructured compounds based on iron or zinc, compatible for application in Aqueous-Based Drilling Fluids (ABF) and Non-Aqueous Drilling Fluids (NAF). Prior Art

[0016] US 4,008,775 describes a process in which porous iron oxide particles are used in drilling muds, primarily aqueous drilling muds, to remove hydrogen sulfide (H2S) released from a wellbore during a drilling operation.

[0017] These iron oxides are described as having an ideal composition of Fe3O4, a particle size of about 1.5 to 60 µm, and a surface area at least ten times larger than magnetite (Fe3O4) particles of equal size.

[0018] WO 82 / 02347 refers to the use of particulate iron oxides in the removal of hydrogen sulfide from non-aqueous liquids such as liquid hydrocarbons.

[0019] The said document provides a process for the removal of H2S from a non-aqueous, substantially anhydrous liquid (hydrocarbon liquid containing said sulfide) comprising contacting the H2S in said liquid with dry or substantially dry iron oxide particles having a surface area of ​​at least 3.5 m 2 / ge composed of a crystalline phase of Fe2O3, Fe3O4 and their combinations together with a fraction of amorphous Fe2O3, said particles being used in a quantity sufficient to reduce the concentration of H2S in said liquid to a predetermined level.

[0020] Contact is maintained for a period sufficient for the formation of stable reaction products, including FeS2(pyrite) and Fe3S4(greigite). Summary of the invention

[0021] The present invention relates to the use of Iron- or zinc-based nanostructured compounds developed for application in water-based drilling fluids (WBF) and non-aqueous drilling fluids (NAF). Furthermore, the present invention evaluates the H2S scavenging capacity of these nanostructured compounds and compares them to conventional metal oxides currently used. Brief description of the figures

[0022] Figure 1 presents a graph showing the behavior (profile) of the H2S concentration in the gas phase over the test time. Conditions: 100% saline solution with 35 g / L NaCl, T = 80ºC.

[0023] Figure 2 shows a graph of the H2S sequestration capacity in relation to the total mass of the evaluated product. Conditions: 100% saline solution with 35 g / L of NaCl, T = 80ºC.

[0024] Figure 3 shows a graph of the H2S sequestration capacity in relation to the mass of Active Matter (AM) of each product evaluated. Conditions: 100% saline solution with 35 g / L in NaCl, T = 80°C.

[0025] Figure 4 presents a graph showing the behavior (profile) of the H2S concentration in the gas phase over the test time with the compounds used in the functionalization of the nanostructures. Conditions: 100% saline solution with 35 g / L NaCl, T = 80°C.

[0026] Figure 5 presents a graph showing the behavior (profile) of the H2S concentration in the gas phase over the test time with 2-aminoethanol at two dosages, 0.3 lb / bbl (0.086 g / L) and 3.0 lb / bbl (8.571 g / L). Conditions: 100% saline solution with 35 g / L in NaCl, T = 80°C.

[0027] Figure 6 presents a graph showing the behavior (profile) of the H2S content in the gas phase throughout the test to evaluate the H2S sequestration capacity in saline solution. Conditions: 100% saline solution with 35 g / L NaCl, T = 80ºC.

[0028] Figure 7 shows a graph of the H2S sequestration capacity in kg of H2S / kg of sequestrant in saline solution. Conditions: 100% saline solution with 35 g / L of NaCl, T = 80ºC.

[0029] Figure 8 shows a graph of the H2S sequestration capacity in kg of H2S / kg of MA (Active Matter) in saline solution. Conditions: 100% saline solution with 35 g / L of NaCl, T = 80ºC.

[0030] Figure 9 presents a graph that shows the behavior (profile) of the H2S content in the gas phase throughout the test to evaluate the H2S sequestration capacity in FBA (Water-Based Drilling Fluid). T = 80ºC.

[0031] Figure 10 shows a graph of the H2S sequestration capacity in kg of H2S / kg of sequestrant in FBA (Water-Based Drilling Fluid). T = 80ºC.

[0032] Figure 11 shows a graph of the H2S sequestration capacity in kg of H2S / kg of MA (Active Material) in FBA (Water-Based Drilling Fluid). T = 80ºC.

[0033] Figure 12 presents a graph that shows the behavior (profile) of the H2S content in the gas phase throughout the test to evaluate the H2S sequestration capacity in FNA (Non-Aqueous Drilling Fluid). T = 80ºC.

[0034] Figure 13 presents a graph of the H2S sequestration capacity in kg of H2S / kg of sequestrant in FNA (Non-Aqueous Drilling Fluid). T = 80ºC.

[0035] Figure 14 shows a graph of the H2S sequestration capacity in kg of H2S / kg of MA (Active Matter) in FNA (Non-Aqueous Drilling Fluid). T = 80ºC.

[0036] Figure 15 presents size data and high-resolution transmission electron microscopy (HRTEM) images of the nanostructures of the present invention. Detailed Description of the Invention

[0037] The present invention proposes the use of nanostructured compounds based on iron or zinc, compatible for application in Water-Based Drilling Fluids (WBF) and Non-Aqueous Drilling Fluids (NAF), with the purpose of sequestering the H2S present in the medium.

[0038] The nanostructured compounds used in this invention are products previously developed by nChemi, which acted as a strategic partner and co-inventor of this innovation. Although commercially available, these nanostructured compounds have been used as H2S scavenging agents in drilling fluids for the first time, both by their developers and in the current technical and scientific literature. Documents exist on the use of metal oxides, such as Zn and Fe, but not the type of nanostructured compound described here, which constitutes an innovation in the sector.

[0039] The nanostructured compounds used in the present invention and their characteristics are described in Table I. These compounds are constituted by an inorganic nucleus that acts as the Active Matter (AM) capable of reacting with H2S, a functionalization compound based on molecules organic compounds and chemically bonded to the inorganic core, called the organic layer, which provides greater stability and dispersibility of the active material, and a solvent chosen to provide greater solubility of the product in the application medium, i.e., FBA or FNA. In addition to the active material, Zn or Fe, the compounds used in the functionalization were also evaluated as H2S scavengers. Table I – Characteristics of Nanostructured Compounds

[0040] The compounds used were produced seeking to obtain a concentration of 50 mg / g of solids (core + functionalization compound) in relation to the solvent, which is equivalent to 5% w / w. Additionally, the active matter content Zn or Fe The expected values ​​for each product are estimates, considering the average mass percentage of functionalization and that the oxide phase is in the stoichiometric ratio. However, deviations from stoichiometry are common in nanoparticles in this size range. The nanostructured compound based on zinc oxide (ZnO) does not present significant functionalization, and in this case, the concentration of the active ingredient corresponds to the mass of zinc in the oxide.

[0041] In addition to the nanostructured compounds of the present invention, for comparison purposes, an H2S scavenger containing 83% w / w monoethyleneamine-triazine (MEA-triazine), conventionally applied in the production environment, was also evaluated under the same experimental conditions.

[0042] The results were also compared with historical data of conventional solid H2S scavengers, applied in drilling fluids, based on zinc oxide (ZnO) and iron oxide in the magnetite phase (Fe3O4), and of an H2S scavenger based on iron (II) gluconate, cited in the State of the Art as an alternative to metal oxides for non-aqueous drilling fluids.

[0043] Table II presents the characteristics of the products used for comparison purposes. It is worth mentioning that the iron oxide found in the sample was magnetite (Fe3O4), although current guidance is to use hematite (Fe2O3) in this type of product to avoid interference with the results obtained from magnetic profiling. Table II - H2S scavengers used as reference and comparison of results Drilling Fluids

[0044] Two drilling fluids were used in the tests, following the same formulations and characteristics as those currently used in the field (Table III). An aqueous solution containing 35 g / L of sodium chloride (NaCl) was inserted into the test matrix as the test fluid. Table III – Drilling fluids used in the evaluation of H2S sequestration capacity

[0045] Table IV presents the typical physicochemical characteristics of the two drilling fluids used in the performance evaluation tests of the nanostructured H2S scavengers of this invention. The aqueous fluid FBA is denser and more viscous than the organic fluid FNA. Table IV – Drilling fluid formulation Table V – Physical-chemical characteristics of the drilling fluids used (1) The electrical stability measurement is only performed on emulsions and is not performed on FBAs. Assessment of physical-chemical characteristics

[0046] To confirm the iron and zinc content in each product, the nanostructured H2S scavenger samples of this invention were characterized by flame atomic absorption spectrometry (FAAS) using an Agilent model 280 FS. The analysis conditions used in the equipment are summarized in Table VI. Table VI - Analysis conditions used in the atomic absorption spectrometer (FAAS)

[0047] To determine these metals in aqueous samples, aliquots of the H2S scavengers were diluted in an aqueous solution acidified with subdistilled nitric acid. Standards were prepared in aqueous medium with five known concentration levels, plus a blank. For the organic sample, preparation involved diluting aliquots of the sample in xylene, as well as the standards used in the tests. The tests were performed in duplicate with the samples, standards, and reagent blanks. Assessment of H2S scavenging capacity

[0048] The evaluation of the capacity of the products in the sequestration of H2S consists of subjecting the reaction medium to a A constant flow of 0.6 L / min of a gas mixture containing 3.2% mol / mol H2S is administered at a known and controlled pressure and temperature. The H2S concentration in the gas phase is measured throughout the test period after passing through the reaction system, using the analytical technique of gas chromatography. After saturation of the reaction medium with the gas mixture, an aliquot of the H2S scavenging product to be evaluated is added at pre-established concentrations. The mass of H2S that each tested product is capable of reducing from the original gas stream indicates the relative scavenging capacity of the products.

[0049] The experimental apparatus used in the tests consists of a 1.0-liter Hastelloy® vessel equipped with instrumentation for monitoring pressure, temperature, and gas flow. Throughout the test, the fluid is kept heated and mechanically agitated.

[0050] The experimental conditions used in the H2S sequestration capacity evaluation tests are designed to approximate field conditions, including solid product dosages. However, previous studies and preliminary exploratory tests indicated superior efficiency of liquid products compared to solids, so a lower dosage was adopted for the liquid products in the comparative tests.

[0051] The experimental conditions adopted in the tests to evaluate the H2S sequestration capacity were: • Temperature: 80°C • Pressure: 5 psig (approx. 20 psia or 0.14 MPa) • Volume: 350 mL • Fluid: Saline Solution with 35 g / L in NaCl • FNA - Non-Aqueous Fluid • FBA - Water-Based Fluid • [H2S] gas: 3.2% mol / mol in balance with CO2 • Seq. Dosage (solid): 3.0 g of solid product, equivalent to 3 lb / bbl (8.571 g / L); • Seq. Dosage (liquid): 0.35 mL of liquid product, equivalent to 0.36 lb / bbl (1.029 g / L). RESULTS Characterization of the evaluated products

[0052] The average active substance content in the nanostructured compounds, obtained from two determinations on different aliquots of each sample, is presented in Table VII and indicates that the zinc concentration is similar to that estimated by the manufacturer (nChemi), then co-owner of this work. For iron, the levels found were lower than initially estimated. The H2S sequestration capacity was calculated using the active substance content actually found in each product. Table VII - Physicochemical parameters evaluated in the products

[0053] The difference observed between the estimated and measured active matter content is typical behavior in nanostructures, due to the stoichiometric relationship not being observed in the composition of crystals at the nanometer scale. The occurrence of flaws in the composition of the crystal lattice results in different values ​​in the ratio of chemical elements in the composition of nanostructured crystals. Additionally, given the characteristics of the samples and the analytical technique employed, it is possible that pre-treatment of the samples for iron analysis, with acid and microwave heating, may eventually yield better recoveries of the elements under study. H2S sequestration capacity of conventional products in drilling fluids, obtained from results of previous studies

[0054] Table VIII presents the results of the H2S scavenging capacity of metal oxides and MEA-triazine, obtained in studies carried out in FBA and FNA drilling fluids, for comparison purposes with the results obtained with the nanostructured products of this invention. Table VIII – Compilation of the results of the H2S scavenging capacity (kg of H2S / kg of Seq.) of the evaluated samples

[0055] These results clearly show the influence of the nature of the fluid on the H2S sequestration capacity of the tested products, since in saline solution the metal oxides showed significantly greater sequestration capacity when compared to real drilling fluids, FBA and FNA. The reduction in the sequestration capacity of the oxides observed in FBA and FNA is possibly associated with the higher viscosity of these fluids and the organic load present in their composition, resulting in encapsulation of the metal oxides, hindering dispersibility in the fluid and, consequently, contact with H2S.

[0056] It is also observed that, in general, zinc oxide presented a higher H2S scavenging capacity than iron oxide. The iron (II) gluconate in organic fluid (FNA) sample presented a lower H2S scavenging capacity, but close to that of iron oxide. H2S scavenging capacity of nanostructured products in drilling fluids A. At a dosage of 0.3 lb / bbl (0.857 g / L) in saline solution

[0057] A first set of tests with the nanostructures was carried out with an exploratory bias using a dosage of 1000 μL / L of the evaluated products, in relation to the volume of liquid in the reaction medium, which is equivalent to approximately 0.36 lb / bbl (1.029 g / L). The behavior of the H2S content in the gas phase throughout the tests is presented in Figure 1, which indicates that the nanostructured products have some H2S sequestration capacity. However, the largest area presented by the product based on the monoethanolamine-triazine compound (MEA-triazine) stands out, signaling the greatest capacity for H2S sequestration. sequestration of H2S from this product in saline aqueous solution containing 35 g / L of NaCl, when compared at the same dosage.

[0058] Table IX presents the results of H2S sequestration capacity in terms of mass of H2S consumed per mass of integral H2S sequestrant used, as well as per mass of active matter (AM) present in each product evaluated, considering the saline solution content presented in Table VII. Table IX – H2S Sequestration Capacity in Saline Solution at a dosage of 0.3 lb / bbl (0.857 g / L)

[0059] Among the products evaluated in saline solution, the product containing 83% w / w MEA-triazine stands out, presenting a higher H2S sequestration capacity (0.5 kg H2S / kg Seq) than the nanostructured products (<0.05 kg H2S / kg Seq), considering the commercial product as supplied. This behavior indicates the need for a smaller volume of the MEA-Triazine chemical product to be shipped to the field to obtain similar results. Figures 2 and 3 represent the H2S sequestration capacity in relation to the whole product and the active matter (AM) content, respectively.

[0060] In terms of active matter (AM) content, it is observed that the H2S sequestration capacity of the products The MA content of nanostructured products OZ and OF-PE is similar to that of MEA-triazine, while OF-PT and OF-AE show higher results than MEA-triazine. These results are promising if it is possible to increase the MA content in nanostructured products, allowing for the shipment of a smaller quantity.

[0061] It is worth mentioning the expectation that OF-PE (0.008 kg H2S / kg Seq), intended for application in aqueous media, would present a higher sequestration capacity than OF-PT (0.020 kg H2S / kg Seq), intended for application in organic media, which was not observed in this set of results. This behavior may be related to the physicochemical characteristics of the component used in the functionalization of the nanostructures and to the interaction of this component with the aqueous fluid, but this relationship was not studied within the scope of the present invention. However, the H2S sequestration capacity of the functionalization compounds was evaluated in saline solution and is presented in item BB Of the functionalization compounds of the nanostructures

[0062] To evaluate the contribution of the components used in the functionalization on the H2S sequestration capacity of the nanostructured product, tests were carried out with 2-aminoethanol, polytetrahydrofuran, and polyethylene glycol, free of metal oxides, and subjected to the same method as the integral product. In the three compounds, the largest expected amount of each functionalization compound was used (Table I), equivalent to a dosage of 3 lb / bbl (8.751 g / L) of integral product, therefore, 40% w / w of polyethylene glycol and polytetrahydrofuran, and 10% m / m of 2-aminoethanol.

[0063] For polyethylene glycol and polytetrahydrofuran, both solid compounds, solutions were prepared with distilled water and ethanol, respectively, at a concentration of 0.4 g / mL, and 1.2 lb / bbl (3.428 g / L) were injected, corresponding to 40% m of the 3 lb / bbl (8.571 g / L) dosage of OF-PE and OF-PT. For 2-aminoethanol, which is already a liquid, a dosage of 0.3 lb / bbl (0.857 g / L) was injected, corresponding to 10% m of the 3 lb / bbl (8.571 g / L) dosage of OF-AE.

[0064] Figure 4 shows the behavior of the H2S content in the gas phase of the test and indicates that polyethylene glycol and polytetrahydrofuran do not present significant H2S sequestration capacity, while 2-aminoethanol presents a measurable H2S sequestration capacity of the order of 0.03 kg of H2S / kg of Seq, which represents a significant portion of what the OF-AE presented in this fluid (0.043 kg / kg).

[0065] However, as can be seen in Figure 5, using an overdose of 3.0 lb / bbl (8.571 g / L); that is, 10 times the dosage of the previous test (0.3 lb / bbl (0.857 g / L)), there is an indication that the H2S sequestered by 2-aminoethanol is returned to the reaction system, signaling that the H2S sequestration reaction may be reversible for this component after saturation.

[0066] In an open drilling fluid circulation system, the reversibility of the reaction poses a major operational occupational health risk to the team of workers on board the rig. C. At a dosage of 3.0 lb / bbl (8.571 g / L) in solution saline

[0067] To improve sensitivity in comparing products, tests were performed in saline solution at a 10-fold higher dosage, approximately 3.0 lb / bbl (8.571 g / L), than the commercial product. This is the typical dosage of conventional metal oxide-based H2S scavengers currently used in drilling environments. The results were compared to the H2S scavenging capacity of MEA-triazine at a dosage of 0.3 lb / bbl (0.857 g / L), typical in production environments.

[0068] Figure 6 shows the behavior of the H2S content in the gas phase over time in one of the three tests performed on each product evaluated, for comparison purposes. The tests were performed in triplicate, and Table X presents the average H2S scavenging capacity of each product evaluated and their respective confidence intervals (t = 1.96, α = 95%). For the products zinc oxide (OxZn), iron oxide (OxFe), and iron(II) gluconate (GlucFe), for which individual tests were performed, the experimental method uncertainty of 10% was adopted for each result obtained. Table X – Average H2S Scavenging Capacity in Saline Solution

[0069] It was found that the injection of nanostructured products at a dosage of 3.0 lb / bbl (8.571 g / L), typical of conventional products currently applied, allows for a better classification of the evaluated products. MEA-triazine (TRIA), even at a dosage of 0.3 lb / bbl (0.857 g / L), showed the highest H2S scavenging capacity, followed by zinc oxide and iron oxide. The results were greater than 0.2 kg H2S / kg Seq, while the nanostructured products showed a scavenging capacity between 0.015 and 0.030 kg H2S / kg Seq Seq, therefore lower than that of conventional solid H2S scavengers (Figure 7).

[0070] Among the nanostructured products, OF-AE presented the greatest capacity for H2S sequestration in saline aqueous solution. However, it was observed that this product presents greater dispersion of the results obtained, and the possible cause for both behaviors is the functionalization component present, 2-aminoethanol, which increases the consumption of H2S from the medium; however, as verified in item B, it can reverse the reaction by returning H2S to the reaction medium.

[0071] The H2S scavenging capacity in relation to the active matter content of each product evaluated is illustrated in Figure 8. It is once again clear that the H2S scavengers OF-AE and OF-PE stand out in relation to the others. However, when compared to the results at a dosage of 0.3 lb / bbl (0.857 g / L), a small reduction in the scavenging capacity of OF-AE and an increase for the OF-PE product are observed, making the greater dispersion of the OF-AE results more evident. D. At a dosage of 3.0 lb / bbl (8.57 g / L) in Fluid of Water-Based Drilling (FBA)

[0072] Figure 9 shows the behavior of H2S in the gas phase, in tests carried out in FBA, and Table XI shows the respective H2S sequestration capacities. MEA-triazine was not evaluated in this fluid and the nanostructured products were compared to conventional metal oxides at the same dosage of 3.0 lb / bbl (8.57 g / L).

[0073] Zinc oxide and iron oxide have the highest H2S sequestration capacity in FBA. However, in a real drilling fluid, the sequestration capacity of nanostructured products approaches that of conventional metal oxides (Figure 10) when compared to the results obtained in saline solution. This confirms a hypothesis put forward in the introduction to this work: that the larger area-to-volume ratio typical of nanostructures provides a greater mass available for sulfide reaction when compared to larger structures. Therefore, it is possible to achieve the same amount of H2S sequestration using a smaller mass of scavenger. Table XI – Compilation of data and results obtained in FBA

[0074] Among the nanostructured ones, OZ, based on zinc nanostructure, stood out, however, with its capacity sequestration capacity even lower than that of zinc oxide. The results indicate that approximately three times the amount of OZ required to be shipped into the field compared to conventional zinc oxide to obtain the same amount of H2S sequestration. On the other hand, this result also indicates the possibility of achieving similar sequestration capacity between these two products if the zinc content in the active ingredient of this product could be tripled, i.e., increasing it from 3.2% w / w to around 10% w / w.

[0075] The same observation can be made regarding OF-AE and OF-PE regarding the increase in active ingredient content. In this case, it would be recommended to increase the iron content from 1% w / w (Table VII) to around 6% w / w, with the expectation of achieving a sequestration capacity similar to that of conventional iron oxide. Naturally, increasing the active ingredient content in nanostructured compounds depends on the product manufacturer's assessment of the technical and economic feasibility of maintaining the other expected physical and chemical characteristics.

[0076] Additionally, the results of H2S sequestration capacity in relation to the active matter content (Figure 11) corroborate the observations already presented, reinforcing that, in addition to the efficiency gain with the increase in the active matter content in the nanostructure, results similar to those of conventional products would be obtained with lower levels of iron and zinc effectively present in the integral product.

[0077] Another bias to be considered concerns the potential ecotoxicity of H2S scavengers used in drilling fluids, since the products Nanostructured products indicate the potential for greater H2S sequestration capacity relative to their mass, which would lead to a lower amount of these elements in spent drilling fluids. Therefore, adjusting the active material content, particularly iron, in commercial nanostructured products could be a way to make this technology more attractive and viable for field application.

[0078] It is also worth mentioning that, in this set of tests, greater variability was observed in the results in triplicate for the nanostructured products, which may be related to the product's stability over time, possibly due to the separation between solvent and nanoparticle, or even between active ingredient and functionalization. This characteristic needs to be considered and evaluated in future studies. E. At a dosage of 3.0 lb / bbl (8.57 g / L) in Non-Aqueous Drilling Fluid (NAF)

[0079] Figure 12 shows the H2S content curves, and Table XII shows the means and confidence intervals obtained (t = 1.96, α = 95%), comparing the behavior of conventional oxides with the nanostructured product OF-PT, in FNA. The OF-PT compound and MEA-triazine were evaluated in triplicate, while the oxides and iron(II) gluconate are individual tests obtained in previous studies under the same experimental conditions. In these cases, to determine the confidence interval, a 10% uncertainty related to the experimental method was adopted.

[0080] It is observed that MEA-triazine, in FNA, has a H2S sequestration capacity 5 to 20 times higher than other products evaluated (Figure 13). Comparing OF-PT with the conventional products, iron oxide and zinc oxide, in the same fluid, it is observed that the nanostructured OF-PT has an H2S sequestration capacity similar to that of iron oxide and approximately half that of zinc oxide, indicating significant potential for achieving results similar to conventional products, with a lower active ingredient content than conventional products. As mentioned previously, increasing the iron content in the active ingredient of OZ, if technically feasible, could lead to performance similar to conventional products, with a lower potential environmental impact. Table XII – Average H2S Sequestration Capacity in FNA

[0081] Since the type of interaction between H2S and functionalized nanoparticles is different from the interaction between traditional Fe3O4 or ZnO particles, due to the presence of organic molecules on their surface, it is necessary to expand the study of the impacts and side effects of nanostructures on the intrinsic characteristics of drilling fluids and their ecotoxicity, in the recovery and / or disposal processes, as well as economic viability, aiming to give sufficient maturity to the technology and enabling its effective application in real scenarios. CONCLUSIONS

[0082] The zinc- and iron-based nanostructured products, when evaluated in water-based drilling fluid (WBF) and non-aqueous drilling fluid (NAF), showed lower H2S scavenging capacity than the respective conventional oxides currently used. However, when compared in terms of active matter content, the behavior is reversed, and the nanostructured products show superior H2S scavenging capacity than conventional products (Figures 11 and 14).

[0083] Under the same experimental conditions, the MEA-triazine-based product demonstrated greater H2S sequestration capacity than the nanostructured products and conventional metal oxides at a dosage 10 times lower. However, when H2S sequestration capacity was evaluated in relation to the active ingredient content, the nanostructured products demonstrated a greater sequestration capacity.

[0084] Among the functionalization components used in the nanostructured products, only 2-aminoethanol showed measurable H2S scavenging capacity, while the others, polyethylene glycol and polytetrahydrofuran, did not show significant reaction capacity with H2S at the evaluated dosages. However, it was observed that 2-aminoethanol, used in the functionalization of the OF-AE compound, has the potential to reverse the scavenging reaction, returning H2S to the reaction medium.

[0085] In FBA, conventional metal oxides showed greater H2S sequestration capacity, however the nanostructured OZ, based on zinc nanostructure, demonstrated promising performance, with the potential to achieve similar sequestration capacity if the zinc content could be increased from 3.2% w / w to around 10% w / w. As currently formulated, it is estimated that approximately three times the amount of OZ would need to be shipped compared to conventional zinc oxide to achieve the same amount of H2S sequestration.

[0086] The OF-AE compound showed greater H2S scavenging capacity than OF-PE in FBA. However, it should be taken into account that the functionalization component of OF-AE, 2-aminoethanol, may have conferred an increase in H2S scavenging capacity; however, with the risk of reversing the reaction with H2S.

[0087] For OF-PE, it is worth mentioning that increasing the active matter content, in this case iron, from around 1% m / m (Table VII) to around 6% m / m, could lead to the H2S sequestration capacity approaching that of conventional iron oxide.

[0088] In FNA, the OF-PT compound exhibits H2S scavenging capacity similar to that of iron oxide and approximately half that of zinc oxide, indicating the potential for achieving results similar to conventional products with lower active ingredient content. This behavior is likely related to the type of interaction between H2S and functionalized nanoparticles, organic molecules, unlike the interaction between particles in conventional Fe3O4 or ZnO products.

[0089] In saline aqueous solution, the OF-PE compound, with polyethylene glycol functionalization and recommended for application in aqueous medium, it presented a lower H2S sequestration capacity than OF-PT, with polytetrahydrofuran functionalization and recommended for application in organic medium.

[0090] Nanostructured products offer the potential to achieve H2S sequestration capacity similar to conventional products, iron oxide and zinc oxide, with a lower active ingredient content compared to conventional products. This approach is related to the potential ecotoxicity of H2S sequestrants used in drilling fluids, as there is a greater performance-to-iron or zinc ratio in the commercial product, which would lead to a lower amount of these elements in the drilling fluids. Therefore, it is possible to achieve the same amount of H2S sequestration using a smaller mass of sequestrant, resulting in logistical gains (transportation and storage) and a reduced environmental impact (reduced use of metals in the process).

Claims

CLAIMS 1. Use of nanostructured compounds based on iron or zinc, characterized for application in Water-Based Drilling Fluids (WBF) or Non-Aqueous Drilling Fluids (NAF) to sequester H2S present in the medium.

2. Use, according to claim 1, characterized by the fact that the nanostructured compounds are constituted by an inorganic core as active matter, a functionalization compound and a solvent.

3. Use, according to claims 1 and 2, characterized by the fact that the inorganic core is selected from the compounds ZnO and Fe3O4.

4. Use, according to claim 3, characterized by the fact that the zinc content in the active matter varies from 3.2% m / m to 10% m / m.

5. Use, according to claim 3, characterized by the fact that the iron content in the active matter varies from 1% m / m to 6% m / m.

6. Use according to any one of claims 1 to 5, characterized in that the size of the inorganic nucleus ranges from 5 to 15 nm. 7.Use, according to claim 1, characterized by the fact that the functionalization compound is selected from 2-aminoethanol, polyethylene glycol, or polytetrahydrofuran.

8. Use, according to claim 7, characterized by the fact that the content of the functionalization compound varies from 10% m / m to 40% m / m.

9. Use, according to claim 1, characterized by the fact that the solvent is water or tetrahydrofuran.

10. Use according to any one of claims 1 to 9, characterized in that the iron- or zinc-based nanostructured compounds have a concentration of 1 to 15% w / w.

11. Use according to any one of claims 1 to 10, characterized in that the nanostructured compounds OZ, OF-AE and OF-PE are applied in Water-Based Drilling Fluids (WBF).

12. Use according to any one of claims 1 to 11, characterized in that the nanostructured compound OF-PT is applied in Non-Aqueous Drilling Fluids (NAF).

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